The biggest issue with the 4.6 is that it's
HUGE!.
Also, the exhaust ports are way angled wrong. It can be done...I'm pretty sure...I'm guessing...I dunno, I'll ask the engineer fella.
While externally the M40 replicates a rather famous '60s racer, the chassis underneath is a thoroughly modern setup. They did manage to put a big block under the MkIIs, and the 4.6 is ... well, dimensionally a bit bigger, but pretty close...
maybe...
Your pal,
Meat.